1. Field of the Invention
The present invention relates to a controller of an internal combustion engine equipped with an electric supercharger that is driven by a motor and, more particularly, relates to a controller that attempts to improve fuel consumption of a vehicle.
2. Description of the Related Art
In recent years, there has been widely known a technology of downsizing which reduces a mechanical loss such as a pumping loss and a friction loss of an internal combustion engine to improve efficiency and fuel consumption of the internal combustion engine, the mechanical loss being reduced by reducing displacement while maintaining output by a supercharger for the purpose of improving the fuel consumption of the internal combustion engine. In order to perform this downsizing, there exists a technique of an electric supercharger in which a motor is mounted on the supercharger; and there is known a technique in which a driving voltage of the motor is changed from existing 12 V to a high voltage of 48 V or 100 V for the purpose of improving the output of the electric supercharger. In this case, a concern is that the amount of charge in a charging device is exhausted for a short period of time unless power generation is performed by a generator for an increase in electricity consumption during operation of the electric supercharger; however, a problem exists in that it is difficult to satisfy both securement of the amount of charge and the output of the internal combustion engine because the generator also uses power of the internal combustion engine.
As countermeasures against such a problem, there has been proposed a technique in which in the case where the amount of charge (state of charge, hereinafter, referred to as “SOC”) in a charging device is sufficient when supercharging by an electric supercharger is needed, power generation is not performed, but the electric supercharger is made to operate by electricity from the charging device; and accordingly, the output of an internal combustion engine is secured. (Patent Document 1)
Furthermore, there has been proposed a technique in which, in a system which includes an electric supercharger and a motor generator that can drive and perform power generation, the motor generator assists the driving of a vehicle when an SOC in a charging device is high, but supercharging by the electric supercharger is performed when the SOC in the charging device lowers; and accordingly, the output of an internal combustion engine is secured. (Patent Document 2)
[Patent Document 1] Japanese Unexamined Patent Publication No. 2011-169286
[Patent Document 2] Japanese Unexamined Patent Publication No. 2005-240580
However, in Patent Document 1, control of the electric supercharger and the generator is performed to secure power of a vehicle in a state where a required supercharging pressure is high and the SOC in the charging device is high, and power generation is always performed during normal supercharging; and therefore, a problem exists in that the operating efficiency and fuel consumption of the vehicle are not taken into consideration.
Furthermore, also in Patent Document 2, control of the electric supercharger and the motor generator is performed, but the control is to secure power of acceleration force or the like by controlling both operation depending on the SOC in the charging device; and therefore, a problem exists in that the operating efficiency and fuel consumption of the vehicle are not taken into consideration.